Their's a bundle kit on newegg.Surpriseingly that's all they have and it's sold out.http://www.newegg.com/Product/Product.aspx?Item=N82E16814998025
The next best thing I would think is this.http://www.buy.com/retail/product.asp?sku=202754374&sellerid=33505864
Although $20 does seem a bit excessive for a SLI Bridge.
Amazon seems a lot better.http://www.amazon.com/s/ref=nb_sb_noss?field-keywords=SLI+Bridge&url=search-alias%3Daps&x=0&y=0
Lol after all of that I finally realized that you should probably just ask Asus.I'm sure they will send you a replacement easily.